Hydrocarbon synthesis



Match 13, 1945. G. l. MA''EER ETAL HYDROCARBON SYNTHESIS patented Mer.13, 1945 George 1. Mateer, mountainside. and Avery n.

George, Cranford, N. J., assignors to Standard Oil Development Company,a corporation of Delaware Application peeemher 11, 1942, serial No.468,658

(o1. 26o-sass.)

6 Claims.

The present invention relates to the production of hydrocarbons fbycatalytic means, said hydrocarbons being highly useful in the supply- Ying of motor fuels or in the production of motor fuels made byalkylation processes. A more particular aspect of the present inventionresides in a combination process in which feed stocks containingisoparafns, normal paramns and olens, both lstraight and branched chain,are subjected to catalytic alkylation reactions to produce alkylateboiling within the motor fuel range in which the relatively inertnormal'parailns are higher aviation fuels is a welcome improvement Y inthe art.

In describing the process, reference will be made chiefly to a crackedrenery C4 cut and one or more of its components, 'butr it is distinctlyto be understood that the presenty invention is not restricted to such afeed stock, it being entirely vpossible to use field butanes which havebeen separated from the reaction mixture, subjectedA action and theremainder going to a catalytic.

dehydrogenation reaction.

In .the petroleum industry it has often been diillcult to adequatelybalanced feed stocks suitable for alkylation so as to produce fromgiven,

quantities of recycle gases available the highest yields of aviationgasoline or high octane number motor fuels by the alkylation method.Paraugmented With oleilns from extraneous sources, to use combined Ce-Csrefinery fractions from cracking operations, or to use Cs fractionsalone which contain isopentane, normal pentane, and the straight andbranched chain oleilns.

The 'operation of the combined isomerizationallo/lation process is suchthat the two processes function substantially as a single unit althoughthe reaction conditions in each of the two processes are independent ofone another. after thefeed stock containing iso and normal paralns andolens is subiectedv to alkylation the reacted mixture is fractionallydistilled to remove a fraction rich in isoparaln reactant, a fractionrich in unreacted normal parafln, and an alkylate. The operation of thefractional distillation may be so controlled as to vary thecompositionof die normal parailin fraction, leaving in it moreor less ofthe isoparailln which is orditicularly in small renery operations theremay be an apparent scarcity of some particular component required in thealkylation reaction.

Thus, for example, isoparafns or the olefin, or both, may be relativelyscarce although large `quantities of basic 'materials from which thesethe refinery gases availableand to Woduce from vthese renery gases thehighly desired alkylate.

above described. The present process Ais designed which utilizes to avmost economical advantage to fully utilize existing refinery gases andto.

accomplish this utilization ina most economical and advantageous manner.

present invention, considerable flexibility in the operation of theseunits is possible. without de- As will be seen .from a fullerunderstanding of the process of the parting from the general principlesof the invention as herein more fully outlined. The prob'- lem hasalways been to improve overall yieldsl of desired products whileutilizing existing4 materials from refining operations. Therefore, anypractical method for the manufacture on a commercial scale of highoctane blending agents for s use in the preparationof octane ,number andnarilyreturned or recycled to the 'alkylation unit. This is carried outfor the reason that when this normal parafdn fraction is conducted tothe isomerization unit, control of the degree or amount o! isomerizationin the present invention is carried out in a novel manner, as follows:

The normal parafiln feed stock-,is heated to a substantially constantpredetermined temperacoming feed stock to that unitand its vaporpressure is likewise determined. A device is employed which is actuatedby the difference in the vapor pressure oi' the incoming feed and theoutgoing reacted mixture, and depending upon the increase `in thepercentage of isobutane contained in the reacted mixture, the valvethrough which the feed stock is introduced into the isomerization unitis 'either opened or closed-by means of .the pressure dierentialactuating means in lorder to control they extent of Vconversion ofnormalto iso butane, so that a substantially constant amount of isoparaiiln isintroduced back into the alkylation unit so as to maintain asubstantially constant source of supply to that unit of isoparailinreacted with olefins to form allwlate. This replacement of reactedisoparaflins is therefore dependent upon the composition of the incomingfeed stock because the rate of introduction of that feed stock iscontrolled by the vapor pressure differential means heretoforedescribed. It is therefore readily understood that one method ofcontrolling that means, or, in other words, of increasing or decreasingthe differential in vapor,pressure, is 'by permitting small or largealiquot portions of isoparaln to be admixed with the normal paraffingoing to the isomerization unit, and this is accomplished by a variationin the fractional distillation conditions maintained in theisoparaffln-normal-parafiin fraction distillation tower. As will be morefully described hereinafter, the

effluent from the isomerization unit goes directly to the alkylationunit or may be returned to and admixed with the alkylated mixture goingto the fractional ldistillation tower for effecting the separation ofisoparan from normal paraiiins and from alkylate.

Although the invention is not restricted to any particular method ofaccomplishing the alkylation reaction, the isomerization reaction and/orthe dehydrogenation reaction, for purposes of illustration it may bestated that the alkylation can be carried out-in the presence ofsulfuric acid of from 90 to 100% concentration. at a temperature betweenabout and about 75 F., under sufficient superatmospheric pressure tomaintain liquid phase operation; that the isoparaifin should be presentin substantial molar excess over the olefins being reacted, and that themix ture should be vigorously agitated to maintain a thorough contactingfor a sufficient period of time to bring the reaction to substantialequilibrium. In the case of the isomerization reaction, a suitablemethodiof carrying it out is to employ aluminum chloride, and in thecase of normal butaneisomerization to use temperatures of between about200 and about 400 F. Likewise, a halogen-containing promoter isdesirable and this may be selected from any one of a number of suitablesubstances, hydrogen chloride being the preferred one. Liquid or vaporphase reaction may be employed and the aluminum chloride maybe depositedon a suitable carrier such as Porocel or other highly porous substancefor greater contacting with the feed stock. In the case of thedehydrogenation unit, the operation may be carried out using a catalystof chromial and alumina gels at atmospheric pressure and under atemperature range of from 1000 to 1400* F., at a throughput of from 100to 1200 volumes of feed stock per volume of catalyst per hour. Each ofthese types of reactions are well known and the speciiic details,specific catalysts and reaction conditions form no part of the presentinvention other than in the combination as shown. As will be more fullyexplained, the invention lies in the subsequent isolation and treatmentof the ei'iluent from the alkylation unit to condition the inerts andunreacted portions of the feed thereto for further use in alkylation.

Referring'to the accompanying drawing, which is a more or lessdiagrammatic representation in sectional elevation of a plant designedfor carrying out the process of the present invention, the

feed stock employed will be, for illustrative purposes only, describedas a cracked refinery C4 A cut containing isobutane, normal butane,normal butylenes and isobutylene.

Such a feed stock is introduced into line 2 by means of open valve 3 andpumps not shown into alkyla'tion unit 4 where it is contacted withsuifuric acid or other suitable alkylation catahrsts. The reactedetlluent, substantially free of acid, emerging therefrom through line 5is fed through open valve 6 into fractionating tower 'I operating undersuch conditions of temperature and pressure wherein a substantially purefraction of isobutane and any lighter boiling hydrocarbons present ispassed overhead through line 8, controlled by valve 9, and recycled backto the feed line 2 for further use in the alkylation unit. It may benecessary at times to purge part of the stream in line 8 in order toprevent appreciable build-up of Ca and lighter components in the reactorby means not shown. A bottoms from this tower I which consists of normalbutane and alkylate, together with small amounts of isobutane, is thenpassed by means of line I0, controlled by valve Il, into line i2 andthen into fractionating column I5 which is operated under conditionseffecting a separation of main quantities of normal butane from thealkylate, it being understood of course that any quantities of isobutanenot; taken overhead from fractionating column 'I are removed with thenormal butane overhead from fractionating column I5. The normal butaneis then, by means of line I5 and open valve Il, conducted to either line4I controlled by valve 42 or line BI controlled by valve 82, or both,depending upon the openings set in valves 42 and 82.

The alkylate, together with any small amounts of normal butane whichhave not been taken overhead to line I6, is withdrawn through line I8controlled by valve I9 and conducted into the final fractionating tower34 for the removal of light alkylate throughline 35 controlled by valve38, medium cut alkylate through line 31 controlled by valve 38, and theheavy bottoms through line 89 controlled by valve 40.

' In operating the alkylation unit, a single stage circulating streamemulsion type of reactor or a two-stage operation in which the olens arefirst absorbed in sulfuric acid and the isoparafn then contacted withthe olefin extract under alkylation conditions may be employed, 'I'hislatter type is advantageous particularly in cases wherein the feed stockdoes not contain only a single olefinic hydrocarbon but may contain Cz,C3, C4

and C5 olens and the like, in which case it may be desirable toselectively extract only the C4 olen or only the Ca olen, as the casemay be, or both, leaving unabsorbed the undesired olen. As stated,two-stage alkylation is preferable in such an instance.

The normal butane, unless removed from the alkylation system tocompensate for the introduction of fresh quantities of normal butane,

builds up indefinitely since it is inert in the alkylation unit, henceat least suflicient normal butane should be removed through line I8 forfurther processing so as to maintain the normal butane level at leastconstant in the alkylation unit and to compensate for the introductionof further quantities of normal butane in the feed stock in line 2. Thisnormal butane, which may contain small or large amounts of isobutane,depending upon the fractionation conditions in fractionating columns Iand I5, is conducted through line 4I controlled by valve 42 into a vaporpressure recording unit 43 having a constant temperature jacket I4. Thevapor pressure is measured for the purpose of the present invention, inthe case of normal butane, at about 100 F. In other words, jacket 44would be maintained about at 100 F. The eliiuent from the heater andconstant temperature zone 43 passing through valve 45 and line 45 goesto' absorber 41 and passes'downwardly therethrough while simultaneouslytherewith there is passing upwardly by means ofy line 50 controlled byvalves il and 5S, hydrogen chloride which is introduced into this sameabsorber by means ofv recycle line 58, and any unabsorbed hydrogenchloride is released from the system through line 48 controlled by valve49. The temperature and throughput maintained in the absorber are suchas to give a hydrogen chloride concentration roughly of from 3 to 20%hydrogen chloride. This fat lid-i 'uor, that is normal butane containinghydrogen chloride, is passed by means of line 52 through control valve58 into the isomerization unit 54. The reacted mixture fromisomerization unit 5d passes through line 55 through open valve 5B intothe stripping tower 51 where, the hydrogen chloride and any lighterdegradation products which may have formed, such as ethane, methane,propane, are removed overhead and recycled to the absorber 41. Thedegradation products, together with any uinabsorbedv hydrogen chloride,are removed from the system through line 48 controlled by valve 49 asheretofore specified. The bottoms from the stripping operation and whichconsist primarily of normal and isobutane are passed through lines 50,53 and open valve BQ into a temperature controlled vapor pressurerecorder 55 similar to that of temperature controlled vapor pressureYrecorder 43 wherein the vapor pressure again at 100 F. is measured, the100 F. temperature being` insured by heating or cooling liquids injacket 55. Vaper pressure recorders 4S and 35 .are conventional pressurerecorder mechanisms with a pneumatic device added which operates toproduce an air pressure output of each recorder having a predeterminedrelation to the respective actual vapor pressures.

4Recorders 43 and S5 may be devices such as those kpage 13,` Figure 22,and Brown Instrument Company Catalogue #8902, page 20. 'I'he output ofcontroller 14 'is connected by means of air line 1I to-a conventionalcontrol-valve 53 such as, for l example, the pneumatic diaphragm controlvalve f type 57T as disclosed in Fischer Governor Com- '.pany Catalogue#35, page F.24. A portion of the reacted emuent free of promoter may'bewithdrawn, if desired, through line 6l, controlled by valve 52, This isusually done, however, only inl cases where an excess of isoparaiin forthe alkylation unitis produced in the isomerization unit. The reactedmixture is passed through line l1 by means of open valve 58 and mayeither be directly introduced with the reacted alkylate emuent, which.is substantiallyv acid-free, into iractionating tower 1 for separationof lisobutane 'fromthe normal butane and alkylate by means of line 89,open valve 10, lin'e S--and openvalve 6, valve 12 being closed, or valve10 may be closed and the mixture-of iso and normal butanes may be passedby means of line 1I and open valve 12 into the feed line 2 and theemuent from the isomerizationunit 54 s thereby fed directly into thealkylation unit 4. Although no provision is made for the'same in thedrawing, nevertheless caustic treaters, driers, pumps, reboilers, andthe like are employed as required. Usually a caustic treat of normalbutane-isobutane eiiiu'ent from the stripping column 51 is employed inorder to neutralize any entrained aluminum chloride or hydrogen chloridecontained therein. Any Cs paramns which have formed duringtheisomerization are removed from the system with the light alkylate asoverhead from tower 04, without the necessity f including anotherfractionating tower in the isomerization section of the system.

That portion of the norlrial butane in line i8 which goes to thedehydrogenation unit is passed through line 8| by means of open valve 82into the dehydrogenation unit 83 and the resulting mixture of olens andparamn content may be either selectively or non-selectively absorbed insulfuric `acid ofv alkylating strength at 2.0-50" F. and at the properacid to olefin ratio in absorber 89 by passing the effluent from line 8dinto the absorber 89 by means of line 85 controlled by valve 86, or theabsorber may be by-passed and the reacted eiiluen-t fed direct to analkylation valve S9 fed into the alkylation unit so that inv effect atwo-stage alkylation is carried out thereby. The normal butane-isobutaneor unabsorbed portion of the eiiluent from the dehydrogenation unit 83is passed by means of line Se controlled by valve 95 tothe isomerizationunit 5t by means of line 4i,-etc., as previously described. Furtherquantities of normal butane may be added tothe eiiluent from theabsorber 89 by-means of line 92vl controlled by valve 93, or if desiredsome or all of the unabsorbed eiiiuent from absorber 89' tion ashereinbefore set forth which may be made without departing from thespirit and scope o! the present invention, and the appended claimsindicate-*only such limitations as should bel im- Whereesiredltobesecured by Letters Patent 'lo is:

- 1. A process for the production of high boiling normally liquidisoparamns which comprises alkylating a hydrocarbonmixture containinglow boiling isoparailin, low boiling normal param-n,

15 low boiling monoolen, under alkylation reacand deviations, variationsand the like, of the invener (to adequately define the invention.v

tion conditions in the presence of an alkylation catalyst to producenormally liquid isoparafllns. separating the unreacted normal parafntrom the alkylate produced, isomerizing sufdcient of said low boilingnormal parafn to isoparain and returning the same to the alkylation unitso as to compensate for and replace the lsoparafn reacted in thealkylation reaction by subjecting the said normal paramn toisomerization in the presence ot an aluminum halide and a,halogencontaining promoter, the rate of throughput of the normalparaffin being correlated with the amount of isoparaflin required -forthe alkylation reaction by measuring the vapor pressure of said lowboiling normal paraffin at a `predetermined temperature, measuring thevapor pressure of the isomerized mixture substantially tree of catalystand promoter at substantially the same predetermined temperature anddirectly controlling the throughput of the feed stock through theisomer-ization reaction zone by means of the vapor pressure differentialbetween the two vapor pressure measurements and conducting the resultingisomerized mixture to the alkylation system.

2. A-process for the production of high boiling normally liquidisoparafns which comprises alkylating a hydrocarbon mixture containinglow boiling isoparaflin, low boiling normal parailln, low boilingmonooleiln, under alkylation reaction conditions in the presence of analkylation catalyst to produce normally liquid isoparaiiins, separatingthe unreacted normal parafn from the alkylate produced, isomerizingsumcient of said low boiling normal paraln to isoparaflin and returningthe same to the alkylation unit so as to compensate for and replace theisoparailin reacted in the alkylation reaction by subjecting the saidnormal parailin to isomerization in the presence of an aluminum halideand a halogen-containing promoter, the rate of throughput of the normalparaffin being correlated with the amount of isoparaflin required forthe alkylation reaction by measuring the vapor pressure 'of said lowboiling normal parain at a predetermined temperature, measuring thevapor pressure of the isomerized mixture substantially free of catalystand Apromoter at substantially the same predetermined temperature anddirectly controlling the throughput of the feed stock through theisomerization reaction zone by means of the vapor pressure diierentialbetween the two vapor pressure measurements, conducting the resultantmixture to the alkylation system, and wherein at least la portion of thenormal paraiiln from the alkylation product is further diverted to acatalytic dehydrogenation unit operated under dehydrogenation conditionsand in the presence of a dehydrogenation catalyst to obtain a productpredominating in monoolefln and normal paraffin, introducing saidproduct into the alkylation reaction zone at least in sufficientquantity to compensate for and balance the loss of oleiin therefrombecause of condensation with isoparafiln. n

3. 'A process for the production of high boiling normally liquidisoparatllns which comprises alkylating a hydrocarbon mixture containinglow boiling isoparamn, low boiling normal paraiiin, low boilingmonoolefln, under alkylation reaction conditions inthe presence of analkylation catalyst to produce normally liquid isoparaflins, separatingthe unreacted normal parainn from the alkylate produced, isomerizingsuillcient of said low boilingnormal parafdn to isoparailln and re.

turning the same to the alkylation unit so as to compensate for andreplace the isoparaiiln reacted in the alkylation reaction by.subjecting the said normal paraiiin to isomerization in the presence ofan aluminum halide and a halogen-containing promoter, the rate ofthroughput of the normal parain being correlated with the amount ofisoparaflin required for the alkylation reaction by measuring the vaporpressure of said low boiling normal paramn at a predeterminedtemperature. measuring the vapor pressure oflthe isomerized mixturesubstantially free of catalyst and promoter at substantiallythe samepredetermined temperature and directly controlling the throughput of thefeed stock through the isomerization reaction zone by means of the vaporpressure differential between the two vapor pressure` measurements,conducting the resultant mixture to the alkylation system, and wherein aportion of the normal paraflin from the alkylation product is sodiverted'to a catalytic dehydrogenation unit operated underdehydrogenation conditions and in the presence of a dehydrogenationcatalyst to give a product containing monoolen and isoparaiiin,absorbing the olefin content of the reacted effluent in sulfuric acid ofalkylating strength and alkylating the resultant extract with isoparain,subjecting the unabsorbed portion of the reacted effluent from thedehydrogenation unit to a catalytic isomerization under isomerizationreaction conditions and conducting' the resultant isomerized mixturesubstantially free of halogen-containing promoter and catalyst to thealkylation reaction.

4. In a process of isomerizing normal paraiiins of at least four carbonatoms per molecule under isomerization reaction conditions in thepresence of an aluminum halide and halogen-containing promoter, theimprovements comprising measuring the vapor pressure of the feed stockat a predetermined temperature, measuring the' vapor pressure of theisomerized mixture substantially free of aluminum halide andhalogen-containing promoter at substantially the same predeterminedtemperature, directly controlling the throughput of the feed stoel;through the isomerization reaction zone by means of the vapor pressurediierential between the two vapor pressure measurements so as toregulate the amount of normal parain passing through the isomerizationreaction zone and the amount of isoparailin produced therein.

5. In a combination alkylation-isomerization process involving thealkylation of a cracked reflnery C4 cut containing butenes and butanes,the amount of isobutane present being adjusted so that it is in molarexcess of the butenes, and

wherein normalbutane is separated from the isobutane by distillationfrom the alkylated reaction mixture, isomerized to isobutane and reintroduced into the alkylation reaction zone, the improvements comprisingregulating the amount and rate of normal butane isomerization toisobutane by measuring the vapor pressure of the feed stock to theisomerization unit at a predetermined temperature, measuring the vaporpressure-of the isomerized mixture substantially free of catalyst andpromoter at substantially the same predetermined temperature, regulatingthe throughput of the feed stock through the isomerization reaction zonedirectly by means of. the vaporpressure differential .between the twovapor-pressure measurements and introducing.

the resultant mixture of isobutane and normal butane into the alkylationsystem.

6. lIn a process of normal parailln isomerization wherein the normalparailin contains at least four crbon atoms per molecule to produceisoparalns under isomerization reaction conditions in the presence of aFriedel-Crafts type catalyst and a halogen-containing promoter, the

-' improvement comprising regulating the rate andv amount of normalparailln fed through the isomerization unit and isomerized therein bymeasuring the vapor pressure of the feed stock at a predeterminedtemperature, measuring the vapor pressure oi' the isomerisedsubstantially free of Friedel-Crafts type catalyst and halogencontainingpromoter at substantially the same predetermined temperature anddirectly control-

